A multiphase fluid is a fluid having more than one phase, such as a fluid having two or more liquid phases or a combination of a gas phase with one or more liquid phases. Flowing multiphase fluids are frequently encountered in industry and it is often necessary or desirable to have the ability to determine their flowing properties as well as flowrates of individual fluids. Unfortunately, however, determining the flowing properties of a multiphase fluid can be difficult for various reasons. Gravity leading to local phase separations, inertia leading to flow detachment and phase separation, and interfacial friction, as well as non-equilibrium gas exholution phenomena occurring within the body of a metering device, affect the ability to obtain reliable and consistent measurements of the flowing properties of multiphase fluids when single phase fluid measurement apparatus and techniques are used.
As a result, there are several conventional approaches to determining the flowing properties of multiphase fluids. For example, some efforts have used Bernoulli's equation to determine the mass flowrate of a multiphase fluid by measuring pressure differentials between different locations in a relatively long conduit. Other efforts involve direct phase density metering which uses a concentrated beam of a specified radiation wavelength exhibiting a specific absorption coefficient for each phase. Various other problems arising with conventional metering devices and methods may include limited application for a specific gas and liquid flow range; gas exholution (indicated as gas previously dissolved in liquid being released in the body of the metering device) leading to errors in calculating densities of the phases due to non-equilibrium gas-liquid dissolution; and ineffectiveness or inaccuracies in determining flow characteristics of each of the gas and liquid phases.
Pipe transportation of a multiphase fluid is typically encountered in the oil and gas industry and power systems handling vapors and condensate. The current method for measuring the total (gas and liquid) transported flowrate and phase ratios of a multiphase fluid involves initially separating the phases using a separator tank, and then metering each separated phase individually. However, this method does not provide real-time, continuous information on flowrates and phase ratios of simultaneously produced oil, gas, and water originating from numerous wells. Typically, produced fluids (i.e., gas and liquid) from only a single well at a time are directed to the separator tank, while produced fluids from other wells must bypass the separator tank to be directed to the field main fluid collector system. Accordingly, there is a need in the art for improved apparatus and methods of mitigating these problems.